Hong Kong's police superintendent warned demonstrators Friday to clear a busy intersection in the city's densely populated Mong Kok district, where pro-democracy protesters clashed with opponents earlier in the day.

Police will begin dismantling protest barriers, and anyone remaining at the site could face arrest, Superintendent Mok Hing-wing said at a news conference broadcast by Hong Kong media.

More pro-democracy protesters arrived at the site after the clashes, and three ambulances went through the crowd to collect injured people.

"I am a little bit scared. I haven't seen anything like this before," one protester told CNN. "We'll do our best to stay calm here, do what we can."

The crowds opposing the protesters in Mong Kok appeared to be angry about the disruption posed by the demonstrations, which have choked one of the busiest intersections in Hong Kong.

"They have been occupying here for a week ... they make everybody angry," another man said. "They can't carry on like this."

Protest leader Joshua Wong told CNN's Kristie Lu Stout that organizers were urging protesters to leave the Mong Kok area and move to the main protest site outside the offices of Hong Kong's chief executive.

The three main groups coordinating the pro-democracy protests responded to the unrest with an ultimatum to authorities.

"If the government does not immediately prevent the organized attacks on supporters of the Occupy movement, the students will call off dialogue on political reform with the government," it read.

The Hong Kong government's second in command, Chief Secretary Carrie Lam, had previously agreed to meet representatives of the Hong Kong Federation of Students to talk about "constitutional development matters," in what many hoped could bring about an end to the political standoff.

Occupy Central, one of the main groups behind the protests, tweeted for supporters in Mong Kok to abandon the site and regroup at the main protest site in Admiralty.

"Must ensure safety is priority in the face of violent attacks," read the tweet.

'Very angry, noisy'

At the scene of the Mong Kok unrest, Joe Lee, a 58-year-old maintenance supervisor, said he was upset about the pro-democracy protesters' presence.

"They've been here for nearly a week. They need to clear out," he said. "It's ruining our economy, they just need to leave."

A middle-aged woman, who did not want to give her name, said she had come out to join the anti-Occupy crowds when she saw footage of protesters' tents being torn down on TV. She said she was furious at "what a mess Hong Kong has become."

Among the pro-democracy protesters, some of whom were crying, 24-year-old Wilson Wong said the crowds were intimidating.

"We just want a peaceful dialogue but we're scared because they're using violence," he said. "We're very nervous and our hands are shaking even as we hold on to each other."

Siu Hay, a 33-year-old musician, said the anti-Occupy crowds were "very angry and very noisy." "They (the Occupy Central protesters) just want peace and democracy."

Responding to the violence, Alex Chow, Secretary General of the Hong Kong Federation of Students, said the unrest was driven by people "with the intention to cause chaos to allow police to clear activists there."

"All supporters of Occupy will abide by the principles of nonviolence," he said. "The chaos is not caused by advocates of Occupy, but by the opposing groups."

The occupation was momentarily cleared enough for police to allow for buses to pass through, to cheers from the crowd.

Stand-off continues

The clash came after a further day of tense stand-offs between authorities and pro-democracy protesters.

Hong Kong's leader, Chief Executive C.Y. Leung, said there was no current plan to clear the remaining protesters, their numbers significantly reduced from the massive crowds that turned out on public holidays the previous two days.

"Currently we do not have any plan, but as I ... said, nowhere else in the world would tolerate protesters surrounding government headquarters indefinitely," he told reporters.

So far, demonstrators and the city's leaders have talked past each other in the streets, in public pronouncements and through the media -- but not directly to one another.

But Leung -- while rejecting the protesters' calls for him to step aside -- has agreed to Chief Secretary Carrie Lam meeting student representatives for a dialogue.

The timing and agenda for the talks have not been announced.

"The dialogue between Carrie Lam and the student federation will be an opportunity to solve the problems," Benny Tai, co-founder of the Occupy Central movement, told journalists late Friday morning.

The protesters would consider the content and the process of the dialogue before deciding what to do next, in light of Leung's failure to have stepped down ahead of the protesters' midnight Thursday deadline, he said.

Protesters should continue the policy of nonviolence and remain cautious, as the police may be trying to provoke a reaction through their tactics, Tai said.

The student federation confirmed the talks, expressing "hope (Lam) will be committed to this city and willing to have an open dialogue."

Taking a swipe at Leung as someone who "has already lost his integrity and ruling legitimacy," the group said "the main focus of the debate should be ... political reform."

With or without talks, the Hong Kong Federation of Students also stressed that its protesters would not leave the streets anytime soon.

"Hong Kong people shall continue its occupying movement until genuine universal suffrage comes to light," the group said, urging supporters to "persevere their occupying action ... and be on guard at all times.

"Whether we will bring our actions to the next level will very much depend on the outcome of the dialogue."

'We don't trust you'

Several dozen police officers were at the scene of protests outside the embattled chief executive's office building Friday morning, carrying helmets, shields and, in a few cases, batons.

As the working day begun, protesters chanted, "It's 9 a.m., where is he?" referring to Leung, and mockingly called the chief executive a "turtle" for refusing to show his face.

Demonstrators blocked two vehicles, which authorities say contained food, water and medical supplies meant for police, from entering the government offices, which the government had declared temporarily closed.